Link rod manufacturing method

ABSTRACT

In a method of manufacturing link rod which integrally joins bushes to each end of pipe-shaped arm portion, an extrusion molded bracket material ( 14 ) is formed to have the length allowing N pieces of the arm portions to be arranged in a horizontal row. Engaging projections ( 7 ) provided on the bracket material ( 14 ) are engaged with ends of the arm portions ( 2 ). Then, the ends of the arm portions ( 2 ) are butted against mounting walls ( 15   a ) provided on a mounting projection ( 15 ) of the bracket material  14 . N pieces of the arm portions ( 2 ) are arranged without clearance in a horizontal row with respect to the bracket material ( 14 ) to form butted portions in the shape of a continuous straight line. The friction stir welding is carried out along the butted portions. Then, the bracket material ( 14 ) is cut into the width of the bracket ( 4 ). The engaging projections ( 7 ) are formed by forming slits ( 18 ) at given intervals on a horizontal projection ( 17 ) extrusion molded integrally with the bracket material ( 14 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing various kindsof link rods being in use for a vehicle suspension or the like.

2. Description of the Related Art

There is publicly known a link rod which has a pipe-shaped arm portionand a bush mounting bracket being friction agitation joined to an end ofthe arm portion. There is also publicly known the art wherein a smalldiameter portion is provided on a mounting projection integrally formedwith a bracket, this small diameter portion is engaged with an end ofthe arm portion and the end of the arm portion comes into butt contactwith the mounting projection so as to be friction agitation jointedalong the butt contact portion. Further, there is publicly known the artwherein a material for the bracket is provided for making a plurality ofbrackets to be cut to a predetermined width in the longitudinaldirection, an end of the arm portion is engaged with height differencewith the bracket material to be sub-assembled, this sub-assembled armportion is arranged in such a manner that a plurality of the armportions are arranged in a horizontal row along the longitudinaldirection of the bracket material, height difference portions of theregions engaged as above are arranged in the shape of a straight lineacross all of the arm portions so that friction agitation joining iscarried out at a time along the height difference portions, andthereafter each of link rods is formed by cutting the bracket materialin a predetermined size of a product in the transverse direction of thebracket material.

Patent reference 1: Japanese patent laid-open publication No. H11-101286

Patent reference 2: Japanese patent laid-open publication No. H11-190375

Patent reference 3: Japanese patent laid-open publication No.H11-099415.

When friction agitation joining the bracket to the arm portion, tooltraveling surfaces in joining regions between both members must beformed in a plane without height difference. Further, in the case wherethe arm portion is formed of pipe member and from the outside thereofthe friction agitation joining is carried out, it is required to keepflush without denting the pipe member due to pressing by the tool.Although these points can be solved by having the mounting projection ofthe bracket engaged with the arm portion so as to form a flush buttportion like the above-described prior art, it is required to make thesmall diameter portion each for one or two brackets with respect to onearm portion and to have it engaged with the arm portion, wherebyproduction efficiency can not be improved. Also in the above mentionedmethod of arranging the arm members for a plurality of link rods in ahorizontal row to join them at a time in a lot, it requires a great dealof time.

SUMMARY OF THE INVENTION

Therefore, the present invention aims to provide the link rodmanufacturing method capable of reliable friction agitation joining andat the same time of improving the production efficiency.

To solve the above-described disadvantages, in accordance with a firstaspect of the present invention, a method of manufacturing a link rodwhich comprises an arm portion having a pair of spaced first and secondwalls parallel extending to each other and a third wall connectingbetween the first and second walls, and a bush mounting bracket beingjoined to an end in the longitudinal direction of the arm portion,wherein a bracket material is extrusion molded and cut in thelongitudinal direction thereof to the length capable of forming aplurality of bush mounting brackets, a plurality of arm portions arearranged in a horizontal row with respect to the bracket material in thedirection of extrusion of the bracket material, each end of the armportions are butted against the bracket material such that such buttedportions extend in the form of continuous straight line, each of the armportions are friction agitation joined to the bracket material along thebutted portions in one process step, and then the bracket material iscut to the width of a bracket, comprises the steps of forming integrallyon the bracket material a horizontal projection which projects in thedirection crossing at a right angle the extrusion direction of thebracket material and extends continuously in the extrusion directionthereof, making vertical slits, each of which has the width allowing endof the third wall to be engaged, on the horizontal projection atpredetermined intervals in the extrusion direction of the bracketmaterial to form a plurality of separate engaging projections, havingthe ends of the third walls engaged with each of the slits and, at thesame time, having the engaging projections fitted into spaces providedbetween the first wall and the second wall on the side of the ends ofthe arm portions, having each end of the first and second walls buttedagainst the bracket material to be made flush with each other to form acontinuous plane tool traveling surface across the arm portions arrangedin a horizontal row.

In accordance with a second aspect of the present invention, the armportion is formed in the shape of a square pipe, a hollow portion openedto an end of the square pipe forms the space provided between the firstand second walls, and the engaging projection is engaged with the hollowportion.

In accordance with a third aspect of the present invention, the firstand second walls are provided each with protrusions protruding from thethird wall in a horizontal direction crossing at right angle thelongitudinal direction of the arm portion, and the space into which theengaging projection is fitted is formed between the protrusions of theneighboring arm portions.

In accordance with a fourth aspect of the present invention, a method ofmanufacturing a link rod which comprises a longitudinally extending armportion having a pair of spaced first and second walls formed inparallel in a cross section crossing at right angles the longitudinaldirection thereof and a third wall connecting between the first andsecond walls, and a bush mounting bracket having a bush mounting holeand being integrally formed with an engaging projection to be engagedbetween the first and second walls on an longitudinal end of the armportion, wherein the bush mounting bracket is friction agitation joinedto and formed integral with the longitudinal end of the arm portion,comprises the steps of forming a bracket material by extrusion moldingsuch that an extrusion has in cross section a configuration of a frontview of the bush mounting bracket when viewed from an axial direction ofthe bush mounting hole and is formed integral with a horizontalprojection which projects in the direction crossing at a right angle thedirection of extrusion and which extends continuously in the directionof extrusion and then by cutting the extrusion in the longitudinaldirection thereof to such a predetermined length that a plurality of thebush mounting brackets are arranged in a horizontal row, forming an armmaterial by extrusion molding such that a cross section of an extrusioncorresponds to a cross section, crossing at a right angle thelongitudinal direction of each of the arm portions, in such a state thata plurality of the arm portions are arranged in a horizontal row, andsuch that the width of the extrusion corresponds to the cutting lengthof the bracket material and then by cutting the extrusion in thelongitudinal direction thereof to a predetermined length of the armportion, making vertical slits, each of which has the width allowing anend of the third wall to be engaged, on the horizontal projection atpredetermined intervals in the extrusion direction of the bracketmaterial to form a plurality of separate engaging projections, arrangingthe bracket material and the arm material in such a state that theextrusion directions of these materials cross at right angle each otherso as to have the ends of the third walls fitted into the slits and atthe same time to have the engaging projections fitted into spacesprovided between the first wall and the second wall on the side of theends of the arm portions, having each end of the first and second wallsbutted against the bracket material to be made flush with each other toform a continuous plane tool traveling surface across the arm portionsarranged in a horizontal row and to form butted portions in the shape ofcontinuous straight line, carrying out friction agitation joining byletting a rotation tool travel on the tool traveling surface along thebutted portions so as to integrate the bracket material with the armmaterial, and then cutting the bracket material and the arm materialinto the width of a product.

According to the first aspect of the present invention, since whenforming the bracket material, the horizontal projection is formedintegral therewith and thereafter the vertical slits are made on thishorizontal projection so as to form the individually separate engagingprojections, the arm portions are sub-assembled one by one with each ofthe engaging projections by fitting each of the engaging projectionsinto the hollow portion provided on the end of the arm portion, and theends of the arm portions are butted against the bracket material, sothat a plurality of the arm portions can be sub-assembled with thesingle bracket material with high positioning accuracy. Also, since allof the arm portions are sub-assembled integrally with the bracketmaterial, the following treatment may be facilitated.

Moreover, merely by making the vertical slits, each of which has thewidth allowing the end of the third wall to be engaged, on thehorizontal projection at the predetermined intervals in the extrusiondirection of the bracket material, two or more engaging projections canbe separated individually. Further, when the ends of the third walls areengaged with each of the slits and when the engaging projections arefitted into the spaces provided between the first wall and the secondwall on the side of the ends of the arm portions, it is possible to besub-assembled. When each end of the first and second walls is buttedagainst the bracket material to be made flush with each other, acontinuous plane tool traveling surface can be formed.

When the sub-assembled arm portions are arranged in a horizontal row,each tool traveling surface is formed in the continuous plane shape withrespect to each of the arm portions, whereby the friction agitationjoining can be carried out on this continuous tool traveling surfacealong the butted portions. Then, since the engaging projections arefitted into the hollow portions on the ends of the arm portions, at thetime of being friction agitation joined, the engaging projectionssupport the ends of the arm portions from the inside thereof to preventdeformation when the arm portions are pressed by the tool, so that thefriction agitation joining may be performed with high reliability.

Further, the sub-assembling operation with high efficiency by assemblingeach of the arm portions and the bracket material with engagingprojections, the joining in one continuous process step between all ofthe arm portions and the bracket material by the friction agitationjoining, then the facilitated separation of each link rod byregular-size cutting the bracket material at relatively short cuttinglength, etc. combine to realize the manufacture with high productionefficiency.

According to the second aspect of the present invention, since the armportion is formed in the shape of square pipe, the hollow portion openedto the end of the arm portion forms the space between the first andsecond walls to allow the engaging projection to be fitted.

According to the third aspect of the present invention, since the firstwall and the second wall of the arm portion each are provided with theprotrusions which extend from the third wall to the direction crossingat right angles the longitudinal direction of the arm portion, thespaces can be formed between the protrusions of the neighboring armportions so as to allow each of the engaging projections to be fittedinto the spaces.

According to the fourth aspect of the present invention, the bracketmaterial and the arm material each of which is extrusion molded in apredetermined size for making a plurality of link rods are arranged insuch a state that the extrusion directions of these materials cross atright angle each other. The engaging projections formed integral withthe bracket material are fitted into between the first wall and thesecond wall of the arm portions. Each end of the first and second wallsis butted against the bracket material. The butted portions are madeflush and have the shape of continuous straight line so as to allow thetool traveling surface of flush continuous plane to be formed. Then,when friction agitation joining the arm material to the bracket materialalong the butted portions and cutting such joined bracket material andarm material into the width of a product, it is possible to manufacturethe link rod easily and efficiently. At this time, since the manufacturecan be carried out using only two kinds of members such as the bracketmaterial and the arm material, the treatment and positioning may befacilitated. Moreover, it is possible to easily form the tool travelingsurface of continuous flush plane along the butted portions, while thefriction agitation joining may be easily performed.

Further, since the engaging projections are formed by making thevertical slits on the horizontal projection formed integral with thebracket material, the ends of the third walls are fitted into the slitsat the time of butting the arm material against the bracket material, itis possible to butt the arm materials with a plurality of the thirdwalls against the bracket material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-A and B are views showing a link rod for a suspension to beobtained by the present invention;

FIGS. 2-A and B are views for explanation of a bracket materialaccording to a first embodiment of the present invention:

FIG. 3 is a view showing an assembling operation at the time ofsub-assembling;

FIG. 4 is a top plan view showing an arrangement of arm portions in ahorizontal row in a sub-assembled state;

FIG. 5 is a view showing ends of the arm portions in the sub-assembledstate;

FIG. 6 is a view showing a state of friction agitation joining;

FIG. 7 is a plan view showing a friction agitation joining process and acutting process;

FIG. 8-A is a view showing an assembling operation according to a secondembodiment and B is a cross sectional view of an arm portion;

FIGS. 9-A and B are cross sectional views schematically showing anotherarm portions;

FIGS. 10-A, B and C are views schematically showing an entire processaccording to a third embodiment;

FIG. 11 is a view showing a sub-assembling method according to the thirdembodiment;

FIG. 12 is a view showing a state of friction agitation joiningaccording to the third embodiment; and

FIG. 13 is a view showing an end surface structure of an arm materialaccording to the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the first embodiment of the present invention will beexplained with reference to the accompanying drawings. FIGS. 1-A and Bshow a link rod to be obtained by the present invention, wherein a viewA is a front view and a view B is a plan view.

This link rod 1 has an arm portion 2 of square pipe configuration and apair of bush 3 which are joined to and integrated with each end in thelongitudinal direction of the arm portion 2. An upper wall and a lowerwall of the square pipe shaped arm portion correspond to a first walland a second wall of the present invention and a right wall and a leftwall correspond to a third wall or third walls. The left and rightbushes 3 are formed identical. It is possible to freely vary the size,the material, etc. with respect to the right and the left bushes 3. Eachof the bushes 3 comprises a bracket 4 of ring shape and a mountingprojection 5 integrally projecting to the radially outward directionfrom a portion of an external periphery of the bracket 4. An end of themounting projection 5 and an end of the arm portion 2 are butted eachother to form a butt portion 6 and joined integral with each other byfriction agitation joining. An engaging projection 7 projecting furtherfrom the mounting projection 5 is press fitted into the end of the armportion 2 in the vicinity of the butt portion 6. Inside of the bracket 4an inner tube 9 is arranged substantially concentrically through theintermediary of a rubber vibration isolator 8. Herein, the structure ofthe bush 3 is optional. For example, the bush may be formed in a doubletube type of inner and outer tubes capable of being press fitted into aring portion of the bracket 4.

FIG. 2-A shows a bracket material 14 for making the bracket 4. Thebracket material 14 is made by extrusion molding light metal such asaluminum alloy, etc. or resin in the direction of an arrow E. Thebracket material 14 is cut into the proper length to make a plurality ofbrackets.

A cross section of the extrusion of the bracket material 14 is the sameas a configuration of the front view (FIG. 1-A) of the bracket 4 and isintegrally provided with a ring-shaped portion and a mounting projection15 which extends radially outwardly from a portion of the ring-shapedportion. The extruding direction E is in coincidence with the directionof an imaginary center line of a bush mounting hole 14 a formed in thebracket material 14. This mounting projection 15 is integrally formedwith the bracket material 14 and extends continuously along the entirelength of the bracket material 14 in the extruding direction E. Further,on the mounting projection 15 there is integrally formed in theprojecting direction thereof a horizontal projection 17 which projectswith height difference in the upward and downward direction with respectthe mounting projection 15. The horizontal projection 17 is formedintegral with the mounting projection 15 in the shape of projectionextending continuously in the direction of extrusion.

In FIG. 2-B, slits 18 are made in the predetermined intervals in thelongitudinal direction of the horizontal projection 17 in such positionsas marked with phantom lines in FIG. 2-A. Each of engaging projections 7is formed on the horizontal projection 17 in an individually separatearrangement between the slits 18. The width (c) of each slit 18 is setto be substantially twice as large as the thickness (t) (see FIG. 1-B)of a vertical wall of the arm portion 2. The width (a) in the verticaldirection and the width (b) in the horizontal direction of each of theengaging projection are substantially identical with the width (a) inthe vertical direction and the width (b) in the horizontal direction ofthe hollow portion 2 c of the arm portion 2 (see FIG. 1-B and FIG. 2-B),respectively.

FIG. 3 shows an assembling state at the time of sub-assembling. The armportion 2 is a square pipe made of the same kind of material as thebracket material 14 and is formed by regular-size cutting an extrusionmolded arm material to the proper length previously. Into an end 2 a ofthe arm portion 2 the engaging projection is fitted. The engagingprojection 7 is formed such as to be tightly fitted into a square hole 2c of the arm portion 2. When sub-assembling the arm portion 2 with thebracket material 14, one end 2 a in the longitudinal direction of thearm portion 2 comes into contact with a mounting wall 15 a (see FIG. 2)on an end of the mounting projection 15. At the same time, the engagingprojection 7 is fitted into the square hole 2 c. The arm portion 2 isarranged in such a state that the extrusion direction of the arm portion2 crosses at right angle the extrusion direction of the bracket material14.

At this time, since the width (c) of each of the slits 18 is twice aslarge as the thickness (t) of each of the vertical wall of the armportion 2, the vertical walls of the neighboring arm portions 2 comeinto contact with each other and are tightly fitted into the slit 18.Therefore, a plurality of the arm portions 2 can be arranged withoutclearance in a horizontal row in the extrusion direction of the bracketmaterial 14. Moreover, since each of the slits 18 functions as aclearance for the end 2 a of the arm portion 2 when the end 2 a isfitted onto the mounting projection 15, the end 2 a of the arm potion 2can be butted against the mounting wall 15 a of the mounting projection15 (see FIG. 6).

Further, since the height H of the arm portion 2 is identical with thevertical width H of the mounting projection 15 (see FIG. 6), when theend 2 a is butted against the mounting wall 15 a, surfaces including thebutted portion in the vicinity of the butted portion can form a flushtool traveling surface. Herein, the other end 2 b of the arm portion 2is engaged with the engaging projection 7 formed on other bracketmaterial 14 so as to be sub-assembled in the similar way as on the sideof the end 2 a.

FIG. 4 is a top plan view showing the arrangement in a horizontal row ofthe arm portions 2 in the sub-assembled state. A plurality of the armportions 2 are arranged in a horizontal row without clearance in theextrusion direction of the bracket material 14. Given that the length ofthe bracket material is L and the width of the arm portion 2 is W1, thewidth W2 of the entire arrangement in the case of arranging N pieces ofthe arm portion 2 in a horizontal row is W1×N, which is set to beidentical with the length L of the bracket material 14. When the end 2 aof each of the arm portions 2 is butted against the mounting wall 15 aof the mounting projection 15, the butted portions 6 between each of thearm portions 2 and each of the mounting projections 15 extendcontinuously in the shape of a straight line which overlaps a joiningline 16 of an imaginary straight line. The friction agitation joining iscarried out along the joining line 16.

FIG. 5 shows the engaged states between the engaging projections 7 andthe ends of the arm portions 2 in a cross-section taken along line 5-5of FIG. 4. As shown in this drawing, the neighboring arm portions 2 arearranged continuously without clearance in a horizontal row and upperand lower surfaces of the arm portions are made flush.

FIG. 6 is a view showing a state of the friction agitation joining. Aprobe 21 of a high speed rotation tool 20 is pressed on the buttedportion 6 thereby to friction agitation join the materials on both sidesof the butted portion 6 so as to be integrated.

Then, since each surface of the mounting projection 15 and the endportions 2 a on both sides of the butt portions 6 forms a tool travelingsurface 22 and is flush without height difference, the frictionagitation joining with high reliability by the rotation tool 30 can becarried out. Moreover, since the butted portions 6 are formedcontinuously across the entire width of the arm portions 2 in ahorizontal row, the entire arm potions 2 can be joined to and integratedwith the mounting projection 15 in one process step by letting therotation tool 20 travel along the joining line 16. Furthermore, sincethe engaging projection 7 is press-fitted into the square hole 2 c ofthe end 2 c, even if the rotation tool 30 is pressed on the end 2 a, theengaging projection 7 supports the end 2 a from the inside thereof sothat the end 2 a can be prevented from denting downward. Therefore, thestable friction agitation joining by the rotation tool 30 can be carriedout with high reliability. Herein, in the case of friction agitationjoining the back side, the whole of the bracket material 14 and the armportions 2 sub-assembled as mentioned hereinabove is tuned over so thatthe back side is friction agitation joined in one continuous processstep in the similar way to the front side.

FIG. 7 is a top plan view for explaining a friction agitation joiningprocess and cutting process. After joining integrally N pieces of thearm portions 2 to a single bracket material 14, the bracket material 14is cut to the width W1 in the direction crossing at a right angle thedirection E of extrusion thereof along the cutting lines F marked with aphantom line, so that each of the link rods is made separately. At thistime, since the cutting length is relatively short, it is possible tocut easily and speedily the bracket material 14. This easy and speedycutting operation and the friction agitation joining in a single processstep combine to manufacture the link rod with high productionefficiency.

FIG. 8 shows the second embodiment wherein an arm portion 2 is not inthe shape of pipe. Since the modification is made only with respect tothe arm portion 2, like reference characters in the former embodimentare used commonly to like or corresponding parts and portions. FIG. 8-Ashows an assembling operation of the arm portion 2. An end 2 a of thearm portion 2 is butted against a mounting wall 15 a of a mountingprojection 15 in a bracket material 14 as shown in FIG. 2-B. Two or morearm portions 2 are arranged in a horizontal row with respect to thebracket material 14. The arm portion 2 is a longitudinally extendingmember having a substantially I-shaped cross section, formed byextrusion molding and regular-size cutting the arm material, and has afirst wall 30, a second wall 31 and a third wall 32. The third wall 32integrally connects in the vertical direction between the first wall 30and the second wall 31 which extend in a pair in parallel with eachother on upper and lower horizontal planes. The thickness (c) of thethird wall 32 is substantially the same as the width (c) of a slit 18.

FIG. 8-B is a cross sectional view of neighboring two arm portions 2 inthe direction crossing at a right angle the longitudinal direction ofthe arm portion 2. The thickness (t) of each of the first wall 30 andthe second wall 31 is substantially identical with the space (t) betweenan engaging projection 7 and each of outer ends of upper and lowermounting walls 15 a of a mounting projection 15 (see FIG. 8-A). Thefirst wall 30 and the second wall 31 each have protrusions 33, 34 eachof which extend laterally from the third wall 32 in the directioncrossing at a right angle the longitudinal direction of the arm portion2. When lateral ends of the extrusions 33, 34 in the neighboring armportions 2 come in contact with each other, a square space 35 is formedby these protrusions 33, 34 and the neighboring left and right thirdwalls 32. This space 35 has the size and the configuration to be tightlyengaged with the engaging projection 7.

Then, as shown in FIG. 8-A, when the arm portions are arranged in ahorizontal row, the engaging projection 7 is fitted into the space 35formed between the neighboring arm portions 2 while fitting the thirdwall 32 into a slit 18. At this time, since the thickness (t) of each ofthe first wall 30 and the second wall 31 on the end 2 a of the armportion 2 is identical with the space (t) formed between each of theouter ends of the upper and lower mounting walls 15 a of the mountingprojections 15 and upper and lower surfaces of the engaging projection7, surfaces in the vicinity of butted portions between the arm portionsand the bracket material 14 forms a flush tool traveling surface.

The tool traveling surface is formed in the shape of a straight linewith respect to each of arm portions 2, and at the same time as shown inFIG. 4, etc., the butted portions 6 extend continuously in a straightline. Therefore, when the tool travels on the tool traveling surfacealong the butted portions 6, the friction agitation joining is carriedout in one continuous process step. Then, since the first upper wall 30and the second lower wall 31 which are being pressed by the tool eachare supported by the engaging projection 7 to be prevented fromdeformation, it can meet the actually required conditions for frictionagitation joining, together with the flush tool traveling surface asmentioned above. In the case where the extrusion material ofsubstantially I-shaped cross section of a relatively moderate price isemployed, the efficient manufacture using the friction agitation joiningalso may be carried out.

FIGS. 10-13 show a third embodiment. FIG. 10 is a view for schematicallyexplaining an entire method of manufacturing a link rod 1. In thedrawing, a view A shows a process of butting each end of left and rightmounting projections 15 provided on left and right bracket materials 14against both ends 12 a, 12 b of an arm material 12, after extrusionmolding the left and the right bracket materials 14 and the arm material12. The bracket material 14 is substantially the same as the one shownin each of the above embodiments. 14 a denotes an integrally formed bushmounting hole. A view B shows a process of friction agitation joining.In the drawing, the left and the right bracket materials 14 and the armmaterial 12 are sub-assembled to form a sub-assembled body 60 in such amanner that the mounting projections 15 of the left and the rightbracket materials 14 are butted against both ends 12 a, 12 b of the armmaterial 12 while having engaging projections 7 fitted into both ends 12a, 12 b of the arm material 12. The friction agitation joining iscarried out by letting a rotation tool 30 travel along a butt line 66between the arm material 12 and the mounting projections 15 so that thearm material 12 and the mounting projections 15 are joined andintegrated together.

Thereafter, by cutting the sub-assembled body 60 into the width of theproduct along cutting lines F, a link rod 1 as shown in a view C isobtained. The view C shows in perspective the link rod 1 which isseparated and finished. 4 a denotes a bush mounting hole. This link rod1 is the same as the one shown in FIG. 8. Therefore, the referencecharacters in the second embodiment are commonly used with respect tothe link rod 1 as a product shown in the view C.

FIG. 11 is a view showing details of the process of FIG. 10-A. The armmaterial 12 is obtained by extrusion molding light metal such asaluminum ally, etc. or resin in the direction of the arrow E such thatthe width of the extrusion corresponds to the one obtained by arrangingin a horizontal row a plurality of arm portions 2 (in this example, 5pieces) as shown in FIG. 10 and by regular-size cutting the extrusion tothe length L2 of the arm portion 2. The width W3 of the extrusion isW1×5 (pieces) wherein W1 is the width of a product, and it correspondsto W2 of FIG. 4.

The arm material 12 has a first wall 12 c, a second wall 12 d and thirdwalls 12 e of substantially rib shape which cross at right angles thefirst and second walls 12 c, 12 d. The first and second walls 12 c, 12 dextend in parallel with each other while having the thirds wall 12 earranged between them. The third walls 12 e extend along the entirelength in the direction of extrusion and are formed with five pieces atregular intervals in the width direction of extrusion. These three wallsare formed integral with each other. Between the neighboring third walls12 e there are formed hollow portions 12 f which pass through the armmaterial 12 in the direction of extrusion. On each end in the widthdirection of extrusion there is provided a groove 12 g which is openedlaterally.

The materials 14 for bracket, substantially the same as the onementioned hereinbefore, are obtained by being extrusion molded and thenby being regular-size cut to the length W1×5, wherein W1 is the width ofa product. This length is equal to L of FIG. 4 and substantiallyidentical to the width W3 of extrusion of the arm material 12. At thetime of extrusion molding, there is integrally formed on a mountingprojection 15 a horizontal projection 17 (see FIG. 10-A) which projectsfrom the mounting projection 15 and extends continuously in thedirection of extrusion. On the horizontal projection 17 there are formedslits 18 at predetermined intervals in the extrusion direction bycutting or the like after the regular-size cutting of the bracketmaterial 14 following the extrusion molding, so as to form engagingprojections 7. The bracket material 14 after forming the slits 18 isidentical with the one shown in FIG. 8-A, and the slits 18 each have thewidth allowing the third wall 12 e to be fitted. The engagingprojections 7 are separated from the neighboring ones by the slits 18and each formed to be tightly fitted into the hollow portions 12 f andthe end grooves 12 g.

The arm material 12 and the bracket materials 14 are butted each othersuch that the extrusion direction E of the arm material 12 crosses at aright angle the extrusion direction E of the bracket materials 14. Then,The third walls 12 e of the arm material 12 are fitted into the slits 18of the bracket material 14. At the same time the engaging projections 7of the bracket material 14 are engaged with the hollow portions 12 f ofthe end grooves 12 g of the arm material 12. At this time the mountingwalls 15 a of the mounting projections 15 butt against end surfaces 12a, 12 b on both ends of the arm material 12, as in the first embodiment.

FIG. 12 is a view showing in enlarged scale the process B shown in FIG.10. Since this sub-assembled body 60 has the friction agitation joiningline (the butt line) 66 which is formed in the shape of continuousstraight line, the friction agitation joining can be smoothly carriedout on this line in one continuous process step. The process of frictionagitation joining is performed in a similar manner as in FIG. 6.Thereafter, the entire length of the sub-assembled body 60 is cut in theextrusion direction of the arm material 12 along the cutting lines Fpassing the intermediate point of the neighboring third walls 12 e, 12 ewith a proper cutter such as a band saw or the like so as to separatethe neighboring link rods 1 (see FIG. 10) from each other. The cuttinglength at this time is L1 (the length of the bracket 4)×2+L2 (the lengthof the arm portion 2).

FIG. 13 is a view showing the end of the arm material 12 viewed from thedirection of extrusion. Each of the engaging projections 7 is engagedbetween the first wall 12 c and the second wall 12 d. Each of the hollowportions 12 f has a horizontally extending rectangular shape in a stateshown in the drawing. F is the cutting line. After the process step offriction agitation joining, the intermediate point between theneighboring third walls 12 e is cut along the cutting line F.

As explained hereinabove, it is possible to easily and efficientlymanufacture the bracket materials 14 and the arm material 12 for aplurality of link rods by extrusion molding. Also, since it is possibleto carry out manufacture using only these three members, the treatmentand the positioning can be facilitated. Moreover, the entire surfaces inthe vicinity of the butted portions 6 along the friction agitationjoining line 66 are made flush, so that it is easy to form thecontinuous flat tool traveling plane so as to easily carry the frictionagitation joining operation. Further, in the process step of frictionagitation joining the same effects as in each of the precedingembodiments can be obtained.

While the present invention has been described in its preferredembodiments, it is to be understood that the invention is not limited toeach of the embodiments but may be otherwise variously modified andchanged within the true scope and spirit of the invention. For example,since for the arm portion it is required to provide a first wall 30, asecond wall 31 and a third wall 32 and to form a space between the firstwall 30 and the second wall 31, the arm portion is not limited to a pipemember but may be formed by a member of I-shaped cross section, H-shapedcross section, etc. An arm member provided with two or more third walls32 and the protrusions as mentioned hereinbefore may be employed. Sucharm members may be easily and cheaply formed by extrusion molding.Therefore, it is not limited to the one of substantially I-shaped crosssection as mentioned hereinbefore but it is possible to employ the onesas shown in FIG. 9-A and B. FIG. 9-A and B are schematic cross-sectionalviews of the arm portions 2. A is an example of the arm portion 2 havingtwo or more third walls 32 a, 32 a. B is an example of the arm portion 2having diagonally crossing walls 32 b, 23 c in addition to the thirdwalls 32 a, 32 a. These are shown simply as examples, and if possible tobe formed by extrusion molding, ones of various shapes of cross-sectionmay be employed. Further, the link rod can be applied to various devicesfor vehicle such as a suspension, an engine mount, etc.

DESCRIPTION OF REFERENCE CHARACTERS

1: Link rod, 2: Arm portion, 3: Bush, 4: Bracket, 5: Mountingprojection, 6: Butted portion, 7: Engaging projection, 14: Bracketmaterial, 15: Mounting projection, 17: Horizontal projection, 18: Slit

1. A method of manufacturing a link rod which comprises an arm portionof longitudinal shape having a pair of spaced first and second wallsparallel extending to each other and a third wall connecting betweensaid first and second walls, and a bush mounting bracket being joined toan end in the longitudinal direction of said arm portion, wherein abracket material is extrusion molded and cut in the longitudinaldirection thereof to the length capable of forming a plurality of bushmounting brackets, a plurality of arm portions are arranged in ahorizontal row with respect to said bracket material in the direction ofextrusion of said bracket material, each end of said arm portions arebutted against said bracket material such that such butted portionsextend in the form of continuous straight line, each of said armportions are friction stir welded to said bracket material along saidbutted portions in one process step, and then said bracket material iscut to the width of a bracket, comprises the steps of forming integrallyon said bracket material a horizontal projection which projects in thedirection crossing at a right angle the extrusion direction of saidbracket material and extends continuously in the extrusion directionthereof, making vertical slits, each of which has the width allowing endof the third wall to be engaged, on said horizontal projection atpredetermined intervals in the extrusion direction of said bracketmaterial to form a plurality of separate engaging projections, havingthe ends of said third walls engaged with each of said slits and, at thesame time, having said engaging projections fitted into spaces providedbetween said first wall and said second wall on the side of the ends ofsaid arm portions, having each end of said first and second walls buttedagainst said bracket material to be made flush with each other to form acontinuous plane tool traveling surface across said arm portionsarranged in a horizontal row.
 2. The link rod manufacturing methodaccording to claim 1, wherein said arm portion is formed in the shape ofa square pipe, a hollow portion opened to an end of the square pipeforms the space provided between said first and second walls, and saidengaging projection is engaged with said hollow portion.
 3. The linkmanufacturing method according to claim 1, wherein said first and secondwalls are provided each with protrusions protruding from said third wallin a horizontal direction crossing at right angle the longitudinaldirection of said arm portion, and the space into which said engagingprojection is fitted is formed between said protrusions of saidneighboring arm portions.
 4. A method of manufacturing a link rod whichcomprises a longitudinally extending arm portion having a pair of spacedfirst and second walls formed in parallel in a cross section crossing ata right angle the longitudinal direction thereof and a third wallconnecting between said first and second walls, and a bush mountingbracket having a bush mounting hole and being integrally formed with anengaging projection to be engaged between said first and second walls onan longitudinal end of said arm portion, wherein said bush mountingbracket is friction stir welded to and formed integral with thelongitudinal end of said arm portion, comprises the steps of forming abracket material by extrusion molding such that an extrusion has incross section a configuration of a front view of said bush mountingbracket when viewed from an axial direction of said bush mounting holeand is formed integral with a horizontal projection which projects inthe direction crossing at a right angle the direction of extrusion andwhich extends continuously in the direction of extrusion and then bycutting the extrusion in the longitudinal direction thereof to such apredetermined length that a plurality of said bush mounting brackets arearranged in a horizontal row, forming an arm material by extrusionmolding such that a cross section of an extrusion corresponds to a crosssection, crossing at a right angle the longitudinal direction of each ofsaid arm portions, in such a state that a plurality of said arm portionsare arranged in a horizontal row, and such that the width of theextrusion corresponds to the cutting length of said bracket material andthen by cutting the extrusion in the longitudinal direction thereof to apredetermined length of said arm portion, making vertical slits, each ofwhich has the width allowing an end of said third wall to be engaged, onsaid horizontal projection at predetermined intervals in the extrusiondirection of said bracket material to form a plurality of separateengaging projections, arranging said bracket material and said armmaterial in such a state that the extrusion directions of thesematerials cross at right angles each other so as to have the ends ofsaid third walls fitted into the slits and at the same time to have saidengaging projections fitted into spaces provided between said first walland said second wall on the side of the ends of said arm portions,having each end of said first and second walls butted against saidbracket material to be made flush with each other to form a continuousplane tool traveling surface across said arm portions arranged in ahorizontal row and to form butted portions in the shape of continuousstraight line, carrying out friction stir welding by letting a rotationtool travel on the tool traveling surface along said butted portions soas to integrate said bracket material with said arm material, and thencutting the joined bracket material and arm material into the width of aproduct.